This invention generally relates to a method of lubricating the components of a drug delivery system and, more particularly, to a method of lubricating a sealing member and a drug holding chamber with a polymeric silicone.
Many drug delivery systems, like syringes, pre-filled syringes, drug cartridges and needleless injectors include an interior chamber for receiving a medicament and a sealing member. The sealing member is usually slidable within the interior chamber and in a fluid-tight relationship with the walls forming the interior chamber.
The sealing member can take many forms, with two conventional forms being a stopper and an O-ring. The sealing members are often made of rubber or elastomeric materials. The interior chamber of many drug delivery systems is made of plastic. The fluid-tight relationship between the sealing member and the wall forming the interior chamber provides a large resistance to movement of the sealing member within the interior chamber. Typically, this resistance has been reduced by pre-treating the walls of the interior chamber and the sealing member with a lubricating solution such as silicone. In the typical coating method, the sealing member is agitated with a solution of the silicone and then the sealing member is removed from the silicone solution and placed in the interior chamber of a drug delivery system. Typically, the surface of the walls of the interior chamber have also been pre-treated with a silicone solution.
There are several disadvantages with the typical lubricating method. The major disadvantage is that the lubricant typically is only loosely adhered to the sealing member or the interior chamber. This loose adherence permits the lubricating solution to become deposited into a medicament loaded in the drug delivery system. In some instances, spheres of silicone have been found suspended within the medicament solution.
Therefore, a drug delivery system that is lubricated in a manner that prevents the lubricant from becoming deposited in the medicament is desirable. This invention includes lubricating the sealing member and the chamber material using techniques that prevent the lubricant from accumulating in the medicament.
In general terms, this invention is a medicament delivery device having two basic components. A chamber has a body made from a plastic material that includes a lubricating substance within the plastic. The chamber includes an inner surface for receiving the medicament. A sealing member is slidably received within the chamber and has an exterior surface that sealing engages the inner surface of the chamber. The sealing member outer surface includes a lubricating silicone substance on the outer surface. The lubricating silicone substance is adhered to the outer surface of the sealing member by cross linking bonds between molecules of the lubricating silicone. The cross linking bonds preferably are formed by irradiating the sealing member after the lubricating silicone has been applied to the outer surface.
In the most preferred embodiment, the lubricating silicone on the sealing member comprises a polydimethyl siloxane having a viscosity of approximately 100,000 centistokes.
The delivery device of this invention preferably is made by the method having the following basic steps. The chamber is formed by mixing a lubricating substance into a plastic material during the process of compounding the plastic material. The chamber is formed from the compounded plastic material that contains the lubricating substance within it. An outer surface of the sealing member is coated with a lubricating substance. The lubricating substance used within the plastic material for the chamber can be, but is not necessarily, the same lubricating substance used on the outer surface of the sealing member. Once the sealing member is coated, the sealing member and the lubricating substance are irradiated to induce cross linked bonds between the molecules of the lubricating substance so that the substance adheres to the outer surface of the sealing member. Then the sealing member is inserted into the chamber so that the outer surface of the sealing member sealingly engages the inner surface of the chamber.